I haven't thought that far as of yet. I'll talk with Aslak and Matt at CukeUp this month. I imagine the same challenge we'll have with composer, they'll have with RubyGems. As of BC break - we have two options - introducing BC layer or waiting for Behat 4.0 release to make a backwards incompatible switch. As of tests - my hands are itching for the last year to sync set of acceptance tests with other implementations, I think that's the way to go